Potato

Phytophthora infestans

A fast-moving water mould that can devastate tomato and potato crops within days under warm, humid conditions. One of the most serious disease risks in the kitchen garden.

Alternaria solani

A common fungal disease that typically appears on older, lower leaves first, causing distinctive concentric ring-patterned lesions. Less aggressive than late blight but can significantly reduce vigour if unchecked.

Streptomyces scabies

A soil-borne bacterial disease causing rough, corky patches on the skin of potato tubers. Purely cosmetic - tubers are safe to eat and flavour is unaffected - but affected skin may need to be peeled more generously.

Pectobacterium atrosepticum

A bacterial disease that causes the stem bases of potato plants to rot and blacken. Infected plants wilt, collapse, and die. Spread through contaminated seed tubers and by water movement in the soil.

Plants are drooping or losing vigour. Most commonly caused by water stress but can also indicate root damage, vascular disease, or heat scorch. Identifying the cause quickly is important as some causes are serious.

Seeds are emerging unevenly or not at all. Usually caused by soil temperature being too low, seeds sown too deep, poor seed-to-soil contact, or old seed stock.

Pythium spp. / Phytophthora spp.

Young seedlings collapse at or just below soil level, caused by fungal pathogens that thrive in overwatered, poorly ventilated growing conditions. Can spread rapidly through a seed tray.

Leaves are turning yellow, which can indicate a range of problems including nutrient deficiency, overwatering, disease, or natural senescence. Identifying whether the pattern is upper or lower leaves, whole leaves or between veins, is key to diagnosis.

Plants are significantly smaller or slower to develop than expected. May be caused by poor soil, nutrient deficiency, root restriction, compaction, pest damage to roots, or disease.

Soft-bodied molluscs that feed on plant material at soil level, most active at night and in wet conditions. A persistent pressure throughout the growing season, especially damaging to seedlings and young transplants.

Shell-bearing molluscs that feed on foliage and young plants, leaving similar damage to slugs. They are more active in mild, damp conditions and tend to shelter in visible daytime hiding spots such as walls, pots, and debris.

Several aphid species colonise potato foliage, weakening plants and acting as vectors for potato viruses including potato leafroll virus and potato virus Y. Colonies tend to establish later in the season than bean blackfly.

Agriotes spp.

Slender, yellowish-brown soil-dwelling larvae of click beetles that tunnel into roots and tubers. Most problematic in ground recently converted from grass or in plots with a long history of soil. Damage is found at harvest rather than visible during the growing season.

General chewing damage from an unidentified pest, leaving holes or missing leaf sections. May be caused by caterpillars, beetles, or other insects. Inspect at dusk to identify the culprit.

General sap-feeding pest activity causing weakened or distorted growth. May be caused by aphids, whitefly, scale insects, or other sucking insects. Inspect leaf undersides and growing tips to identify the pest.

Damage to roots, tubers, or underground plant parts from soil-dwelling pests such as vine weevil larvae, leatherjackets, chafer grubs, or wireworm. Plants often show no above-ground symptoms until damage is severe.